KR20110049259A - Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same - Google Patents

Abstract

PURPOSE: A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided to improve battery characteristics and lifetime property of the rechargeable lithium battery due to excellent adhesive force to a current collector. CONSTITUTION: A negative electrode for a rechargeable lithium battery includes a current collector(2) and a active material layer(3) formed on the current collector. The active material layer is formed of active materials capable of forming a solid of metal M and a lithium-containing compound, wherein M is selected from Cu, Ti, Cu-X alloy, Ti-X alloy, and their mixture, wherein X is alkali metal, alkali earth metal, group 13 elements, group 14 elements, transition metal, rare earth metal, and their combination.

Description

A negative electrode for a lithium secondary battery and a lithium secondary battery including the same {NEGATIVE ELECTRODE FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING SAME}

The present disclosure relates to a negative electrode for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Lithium secondary batteries, which have been popular as power sources for portable electronic devices in recent years, exhibit a high energy density by using an organic electrolytic solution and exhibiting discharge voltages two times higher than those of conventional batteries using an aqueous alkaline solution.

As a cathode active material of a lithium secondary battery, an oxide composed of lithium and a transition metal having a structure capable of intercalating lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNi _1-x Co _x O ₂ (0 <X <1) Was mainly used.

Lithium metal was initially used as a negative electrode active material. However, due to a problem of dendrites occurring and a very short lifespan, various types of carbon-based carbonaceous materials including artificial graphite, natural graphite, and hard carbon, which can be inserted / desorbed of lithium, have recently been used. The material is being used. However, the carbon-based anode active material can solve the problem of dendrites and has excellent voltage flatness and good life characteristics at low potential, but due to high reactivity with the organic electrolyte and low diffusion rate of lithium in the material, power ( There are problems such as power characteristics, initial irreversible control, and electrode swelling during charging and discharging.

Accordingly, researches for using lithium alloy as a negative electrode active material to solve the problem of the dendrite has a long life. U. S. Patent No. 6,051, 340 describes a negative electrode comprising a metal that is not alloyed with lithium and a metal that is alloyed with lithium. In this patent, a metal that is not alloyed with lithium acts as a current collector, and a metal that is alloyed with lithium forms an alloy with lithium ions that have escaped from the anode during charging, and the alloy serves as a negative electrode active material, and the cathode Silver will contain lithium when charged. However, even with the lithium alloy described above, it was difficult to obtain satisfactory battery characteristics.

In addition, silicon, tin, or a compound thereof has also been studied as a material that can replace the carbon-based material used as the negative electrode active material. However, the silicon or tin has a problem of large irreversible capacity, and in particular, silicon has a problem of severe shrinkage and expansion as the charging and discharging cycle progresses, so that the negative electrode active material is dropped, thereby deteriorating the life characteristics of the lithium secondary battery. The tin oxide proposed by Japan's Fujifilm Co., Ltd. was spotlighted as a new material to replace the carbon-based negative electrode active material, but the initial coulombic efficiency was lowered to 30% or less, and lithium-tin alloy was formed by the continuous charge and discharge Due to the reduced capacity and low life characteristics, it is not practical.

The positive electrode and the negative electrode of the lithium secondary battery are prepared by mixing such an active material, a binder, and optionally a conductive material to prepare a slurry type composition, and applying the composition to a current collector. At this time, aluminum is mainly used for the positive electrode as the current collector, and copper is mainly used for the negative electrode.

Recently, studies for further improving the energy density of lithium secondary batteries have been conducted.

Embodiment of the present invention is to provide a negative electrode for a lithium secondary battery excellent in buffering effect on the volume change of the active material.

Another embodiment of the present invention is to provide a method for producing a negative electrode for a lithium secondary battery.

Another embodiment of the present invention is to provide a lithium secondary battery including the negative electrode for the lithium secondary battery, and excellent in energy density and life characteristics.

According to one embodiment of the present invention, a current collector and an active material layer formed on the current collector, the active material layer is a solid solution of metal M (the M is Cu, Ti, Cu-X alloy, Ti-X alloy ( X is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, or combinations thereof, and not selected from Cu and Ti) or combinations thereof, and lithium The negative electrode for a lithium secondary battery which consists of an active material which can form a compound is provided.

The active material layer may have a porosity of 10 to 70% by volume.

When the solid solution of the metal M is represented by a chemical formula, L _x N _y (L may be Cu, Ti, or a combination thereof, N is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, or a rare earth element). Or a combination thereof, and not Cu and Ti, x is 70 to 100% by weight and y is 0 to 30% by weight.

The active material may be Si, Sn, Si-Q1 alloy, Sn-Q2 alloy (wherein Q1 and Q2 are independently of each other alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof Element, and not Si and Sn) or a combination thereof.

According to another embodiment of the present invention, an active material capable of forming a lithium-containing compound and a metal M (The M is Cu, Ti, Cu-X alloy, Ti-X alloy (The X is alkali metal, alkaline earth metal, Group 13 An element selected from an element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, but not Cu and Ti), or a combination thereof) to prepare a mixture by mixing powder and collecting the mixture It provides a method of manufacturing a negative electrode for a lithium secondary battery comprising the step of thermally spraying on the whole to form an active material layer.

The active material powder may have an average particle size of 100 nm to 1 μm, and the metal M powder may have an average particle size of 100 nm to 1 μm.

The active material powder and the metal M powder may be mixed in a weight ratio of 30:70 to 70:30.

The thermal spraying step may be carried out by a method selected from plasma spraying, arc spraying, ultrafast flame spraying, gas spraying, or a combination thereof.

In addition, the thermal spraying process may be carried out at a temperature of 10000 to 18000 ℃, the mixture may be sprayed at a spraying speed of 100 to 400m / sec when spraying.

According to another embodiment of the present invention, there is also provided a lithium secondary battery comprising the negative electrode and the electrolyte.

The negative electrode for a lithium secondary battery according to the embodiment of the present invention has the expansion of the active material due to the charge and discharge is suppressed and has excellent adhesion to the current collector, resulting in improved battery characteristics and life characteristics of the lithium secondary battery when the application of the battery. .

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, but the present invention is not limited thereto, but is defined only by the scope of the claims to be described later.

In a lithium secondary battery, active materials in the electrode contract and expand as charge and discharge proceed. In particular, the volume change of the silicon-based negative electrode active material is severe. Such a change in the volume of the active material has a problem of causing a decrease in the life characteristics of the lithium secondary battery.

On the other hand, in one embodiment of the present invention, by thermally spraying a mixture of the active material and the metal powder to form an active material layer, the battery and life characteristics of the lithium secondary battery are exhibited by exhibiting a buffering effect on the volume change of the active material due to charge and discharge. Can be improved.

That is, the negative electrode for a rechargeable lithium battery according to one embodiment of the present invention includes a current collector and an active material layer formed on the current collector, and the active material layer is a solid solution of metal M (wherein M is Cu, Ti, and Cu-X). Alloy, Ti-X alloy (wherein X is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements or combinations thereof, but not Cu and Ti) or combinations thereof Selected), and an active material capable of forming a lithium-containing compound.

That is, the active material layer does not contain a conductive material and a binder, and is composed of only an active material capable of forming a lithium-containing compound and a solid solution of metal M. Expressed in the formula, the active material layer is composed only of a mixture of A and B. In this case, A is an active material capable of forming a lithium-containing compound, B is a solid solution of the metal M, when the solid solution of the metal M is represented by the formula, L _x N _y (L may be Cu, Ti or a combination thereof) N is an element selected from alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, not Cu and Ti, x is 70 to 100% by weight and y is Metal solid solution of 0 to 30% by weight).

1 is a cross-sectional view of a negative electrode for a rechargeable lithium battery according to one embodiment of the present invention, but the present invention is not limited thereto. Referring to FIG. 1, a lithium secondary battery negative electrode 1 according to an aspect of the present invention includes a current collector 2 and an active material layer 3 formed on the current collector 2. Pores 4 are present in the active material layer.

The current collector 2 may be a copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam (foam), copper foam or a polymer substrate coated with a conductive metal. Specific examples of the current collector may be copper foil or nickel foil.

The polymer is selected from polyethylene terephthalate, polyimide, polytetrafluoroethylene, polyethylene naphthalate, polypropylene, polyethylene, polyester, polyvinylidene fluoride, polysulfone, copolymers thereof or combinations thereof. Can be used.

The active material layer 3 is positioned on the current collector 2.

The active material layer 3 is a solid solution of metal M (the M is Cu, Ti, Cu-X alloy, Ti-X alloy (the X is alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth) Element selected from an element or a combination thereof, not Cu and Ti) or a combination thereof, and an active material capable of forming a lithium-containing compound.

The negative electrode for a rechargeable lithium battery according to one embodiment of the present invention is formed by thermally spraying a mixture of an active material capable of forming a lithium-containing compound and a metal M powder onto a current collector, and the mixture of the injected active material powder and the metal powder has a high temperature. The metal powder melts completely as a whole while passing through the heat source, and the active material powder collides with the current collector while the surface is molten. That is, in one embodiment of the present invention, the active material powder is not completely melted entirely, only the surface is melted, and the metal powder is completely melted entirely. At this time, the surface-melted active material particles are brought into contact with each other, and the molten metal powder is completely melted. As a result, the surface-melted active material particles are lodged into the completely molten metal powder and are present on the current collector. As a result, since the active material is strongly connected by the metal, the expansion of the active material can be suppressed, and the metal also plays a role of the binder and the conductive material, and thus it is easy without using the conductive material and the binder used in the formation of the active material layer. The negative electrode can be prepared.

In general, an active material particle such as Si and a metal are easy to form an intermetallic compound, and if the intermetallic compound is formed and the intermetallic compound is brittle, there is a problem that the mechanical strength is remarkably low. Since it enables rapid melting and cooling, the formation of the intermetallic compound of the active material particles and the metal can be suppressed.

In addition, pores are formed in the active material layer prepared as described above by welding the active material powder and the metal M powder. In this case, the active material layer formed may have a porosity of 10 to 70% by volume, and may also have a porosity of 20 to 50% by volume. When the porosity in the active material layer is included in the above range, the buffering effect according to the volume change of the active material layer is appropriate, the electrolyte solution is also easily penetrated, and the appropriate mechanical strength can be maintained.

In addition, since the active material particles and the metal are bonded to each other and exist in the form of an alloy, the active material layer has excellent mechanical strength as compared with an active material layer composed of an organic material of a conventional conductive material and a binder.

In addition, the active material layer may exhibit excellent peeling strength with respect to the current collector because the metal powder is attached to the current collector in the state of surface melting.

In addition, a material capable of forming a lithium-containing compound may be used as the active material. Representative examples of the active material include Si, Sn, Si-Q1 alloy, Sn-Q2 alloy (Q1 and Q2 are independently of each other alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or their Element selected from combinations, not Si and Sn), or combinations thereof.

Q1 and Q2 are independently of each other Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Specific examples of the active material include Si or Sn.

The active material may be included in an amount of 50 wt% or more based on the total weight of the active material layer, and may be included in an amount of 60 to 70 wt%. When the content of the active material layer is 50% by weight or more, an appropriate battery capacity may be exhibited.

Examples of the metal M include Cu, Ti, Cu-X alloys, and Ti-X alloys (wherein X is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof. , And not Cu and Ti) or a combination thereof. In addition, X is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Ru, Os, Hs, Rh, Ir, Pd, Pt, Ag, Au, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. Specific examples of X include Mg, Al, or a combination thereof. When the metal M is represented by a chemical formula, L _x N _y (L may be Cu, Ti, or a combination thereof, N may be an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, or An element selected from a combination thereof, not Cu and Ti, x is 70 to 100% by weight, and y is 0 to 30% by weight.

The negative electrode for a rechargeable lithium battery according to one embodiment of the present invention having the structure as described above is an active material powder and a metal M capable of forming a lithium-containing compound (the M is Cu, Ti, Cu-X alloy, and Ti-X alloy ( X is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and not Cu and Ti). And thermally spraying the mixture onto a current collector to form an active material layer.

2 is a process chart briefly showing a manufacturing process of a negative electrode for a rechargeable lithium battery according to one embodiment of the present invention. Referring to Figure 2 in more detail, first to prepare a mixture by mixing the active material powder and metal M powder capable of forming a lithium-containing compound (S1).

The active material is the same as described above.

The active material powder may be used having an average particle size of 100nm to 1㎛, may be used having an average particle size of 200nm to 500nm. When the average particle size of the active material powder is included in the above range, the active material structure can be maintained while maintaining the initial efficiency, so that the cycle life characteristics can be better maintained.

The metal M powder is also the same as described above.

The metal M powder may be one having an average particle size of 100 nm to 1 μm, and one having an average particle size of 200 nm to 500 nm. When the average particle size of the metal M powder is included in the above range, the bonding between the active materials is easier, and does not exhibit adverse effects such as covering the surface of the active material and the reversible efficiency and so on.

The active material powder and the metal M powder as described above may be mixed in a weight ratio of 30:70 to 70:30, or may be mixed in a weight ratio of 40:60 to 60:40. When the mixing ratio of the active material powder and the metal M powder is included in the above range, the capacity and the heating efficiency can be maintained well while appropriately securing the conductivity.

The mixture of the prepared active material and the metal powder is thermally sprayed on the current collector to form an active material layer (S2).

The current collector is the same as described above.

The thermal spraying process is a method that does not significantly affect the properties of the raw material powder and the current collector, plasma spraying method, arc spraying method, high velocity oxygen fuel spraying (HVOF), gas spraying method, etc. There is this.

The thermal spraying process as described above is easy to work in the air, it is possible to easily control the state of the active material layer generated by adjusting the spraying speed, temperature and the like of the powder.

In order to manufacture a negative electrode for a rechargeable lithium battery according to one embodiment of the present invention, the heat spraying process may be performed at a temperature of 10000 to 18000 ° C, or may be performed at a temperature of 12000 to 15000 ° C. When the thermal spraying process is performed at the above temperature, sufficient surface melting of the active material and the metal powder may occur, and as a result, a solid solution of the active material and the metal may be easily produced, and an active material layer having an appropriate porosity is formed. can do.

In addition, the injection speed of the mixture of the active material and the metal during the thermal spraying process may be 100 to 400m / sec, may be 200 to 300m / sec. When the spraying speed falls within the above range, a solid solution of the active material and the metal in the mixture can be appropriately formed, and an active material layer having an appropriate porosity can be formed, and the surface melting of the active material and the metal powder is sufficient. Can be generated, and as a result, a solid solution of the active material and the metal can be easily produced.

The mixture of the active material and the metal M powder passes through the heat source by the thermal spraying process, so that the surfaces of the powders collide with the current collector in a molten state, thereby forming an active material layer including pores on the current collector 2 in the form of a solid solution. 3) to form a negative electrode (S3) for the lithium secondary battery as a result.

In this case, since the metal having excellent electrical conductivity is uniformly enclosed around the fine active material, excellent conductivity can be exhibited, and excellent adhesion to the current collector can be obtained, so that a separate conductive agent and a binder are unnecessary. In addition, since the active material is strongly connected to the metal, expansion of the active material due to charge and discharge can be suppressed.

As a result, the negative electrode for a lithium secondary battery manufactured by the manufacturing method as described above may exhibit high capacity and long life characteristics.

According to another embodiment of the present invention provides a lithium secondary battery including the negative electrode.

3 is a schematic cross-sectional view of a rechargeable lithium battery according to another embodiment of the present invention.

Referring to FIG. 3, the lithium secondary battery 10 is impregnated with a positive electrode 20, a negative electrode 30, and a separator 40 existing between the positive electrode 20 and the negative electrode 30. The battery container 50 containing electrolyte solution, and the sealing member 60 which encloses the said battery container 50 are included.

The cathode 30 is the same as described above.

The positive electrode 20 includes a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer includes an active material capable of electrochemical redox.

As the cathode active material, a compound (lithiated intercalation compound) capable of reversible intercalation and deintercalation of lithium may be used. As a representative example, one or more of a complex oxide of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. Specific examples of the positive electrode active material may be a compound represented by any one of the following formula:

Li _a A _1-b X _b D ₂ (wherein 0.95 ≦ a ≦ 1.1, and 0 ≦ b ≦ 0.5); Li _a A _1-b X _b O _2-c D _c (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5 and 0 ≦ c ≦ 0.05); Li _a E _1-b X _b O _2-c D _c (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a E _2-b X _b O _4-c D _c (wherein 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b X _c D _α (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Co _b X _c 0 _2-α T _α (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Co _b X _c 0 _2-α T ₂ , wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2; Li _a Ni _1-bc Mn _b X _c D _α (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Mn _b X _c 0 _2-α T _α (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Mn _b X _c O _2-α T ₂ (wherein 0.95 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.9, and 0.001 ≦ d ≦ 0.2); Li _a Ni _b Co _c Mn _d G _e O ₂ (wherein 0.90 ≦ a ≦ 1.1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and 0.001 ≦ e ≦ 0.2); Li _a NiG _b O ₂ (wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.2); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 3); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); LiFePO ₄

In Chemical Formulas 1 to 24, A is selected from Ni, Co, Mn, or a combination thereof; X is selected from Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D is selected from O, F, S, P, or a combination thereof; E is selected from Co, Mn, or a combination thereof; T is selected from F, S, P, or a combination thereof; G is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, Si, Ge, Sn, P, As, Sb, Bi, S, Se, Te, Po, Fe, Sr, or a combination thereof; Q is selected from Ti, Mo, Mn, or a combination thereof; Z is selected from Cr, V, Fe, Sc, Y, Ti, or a combination thereof; J is selected from V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, what has a coating layer on the surface of this compound can also be used, or the compound and the compound which has a coating layer can also be used in mixture. The coating layer may comprise at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used. The coating layer forming process may use any coating method as long as it does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

The positive electrode active material layer may further include a binder for improving adhesion to the current collector, a conductive material for improving electrical conductivity, and the like.

The binder may be polyvinyl chloride, polyvinyl difluoride, polymer containing ethylene oxide, polyvinyl alcohol, carboxylated polyvinylchloride, polyvinylidene fluoride, polyimide, polyurepan, epoxy resin, nylon Or at least one selected from the group consisting of carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber and acrylated styrene-butadiene rubber Can be.

As the conductive material, any battery can be used as long as it is an electronic conductive material without causing chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, Metal powders, such as aluminum and silver, metal fiber, etc. can be used, and also conductive materials, such as a polyphenylene derivative, can be mixed and used.

In the positive electrode 20 having the above-described configuration, a positive electrode active material, a binder, and optionally a conductive material are mixed in a solvent to prepare a composition for forming a positive electrode active material layer, and then, the positive electrode active material layer forming composition is applied to a current collector. After dry rolling can be prepared. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

The positive electrode active material, the binder, and the conductive agent are the same as described above.

N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

The current collector may be selected from the group consisting of aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam (foam), copper foam, a polymer substrate coated with a conductive metal, and combinations thereof, Aluminum foil can be used suitably.

As the electrolyte to be charged in the lithium secondary battery, a lithium salt dissolved in a non-aqueous organic solvent may be used. The lithium salt acts as a source of lithium ions in the battery to enable operation of the basic lithium secondary battery. Specific examples of the lithium salt include LiSbF ₆ , LiAsF ₆ , LiClO 4, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , Li _S O ₃ CF ₃ , LiCl, LiI, LiB (C ₂ O ₄ ) ₂ , Li [N (SO ₂ CF ₃ ) ₂ ], Li [N (SO ₂ CF ₂ CF ₃ ) ₂ ], or a mixture thereof.

The concentration of the lithium salt may be used in the range of 0.6 to 2.0 M, and may be used in the range of 0.7 to 1.6 M. If the concentration of the lithium salt is included in the above range, it can maintain an appropriate viscosity, it can exhibit excellent electrolyte performance and mobility of lithium ions.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, alcohol, protic or aprotic solvent. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), etc. may be used. The ester solvent may be n-methyl acetate (MA), n-ethyl acetate (EA), n-propyl acetate (PA). , Dimethyl acetate (DME), methyl propionate (MP), ethyl propionate (EP), γ-butyrolactone (GBL), decanolide, valerolactone, mevalonolactone , Caprolactone, and the like can be used. As the ether, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used, and cyclohexanone may be used as the ketone solvent. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent, and diglyme (DGM), tetraglyme (TGM), etc. may be used as the protic solvent. In addition, the aprotic solvent is a nitrile such as T-CN (wherein T is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double bond aromatic ring or an ether bond). Ryu; Amides such as dimethylformamide and dimethylacetamide; Dioxolanes such as 1,3-dioxolane (DOX); Sulfolane; Cyclohexane and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of 1: 1 to 1: 9, so that the performance of the electrolyte may be excellent.

In the lithium secondary battery according to the exemplary embodiment of the present invention, the non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent in the carbonate solvent. In this case, the carbonate solvent and the aromatic hydrocarbon organic solvent may be mixed in a volume ratio of 1: 1 to 30: 1.

As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound represented by the following Formula 25 may be used.

[Formula 25]

(In Chemical Formula 25, R ₁ to R ₆ are each independently selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and a combination thereof.)

Specific examples of the aromatic hydrocarbon organic solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 , 2,4-trichlorobenzene, iodobenzene, 1,2-dioodobenzene, 1,3-dioiobenzene, 1,4-dioiobenzene, 1,2,3-triiodobenzene, 1, 2,4-triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluor Rotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1, 2,4-trichlorotoluene, iodotoluene, 1,2-dioodotoluene, 1,3-diaodotoluene, 1 , 4-diaiodotoluene, 1,2,3-triiodotoluene, 1,2,4-triiodotoluene, xylene, and combinations thereof.

The electrolyte may further include an additive in which the electrolyte is typically used for improving battery characteristics. Specifically, in order to improve the thermal safety of the lithium secondary battery, an ethylene carbonate-based compound having a structure of Formula 26 may be used:

[Formula 26]

(In Formula 26, R ₇ and R ₈ are each independently selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and a fluorinated C1-5 alkyl group, wherein X And at least one of Y and halogen is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ), and a fluorinated alkyl group having 1 to 5 carbon atoms.)

Specific examples of the ethylene carbonate-based compound having the structure of Formula 26 include ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate and nitroethylene And a compound selected from the group consisting of carbonates, cyanoethylene carbonates, and mixtures thereof. Among these, fluoroethylene carbonate can be used suitably.

The content of the ethylene carbonate-based additive is not particularly limited, but may be appropriately added in a range capable of obtaining a thermal stability effect.

The separator 40 may exist between the positive electrode and the negative electrode according to the type of the lithium secondary battery. As the separator 40, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene Of course, a mixed multilayer film such as a polypropylene three-layer separator can be used.

Hereinafter, examples and comparative examples of the present invention are described. However, the following examples are only examples of the present invention, and the present invention is not limited to the following examples.

Example 1 Preparation of Negative Electrode

Si powder having an average particle diameter of 200 nm and Cu powder having an average particle diameter of 1 μm were mixed at a weight ratio of 40:60 to prepare a mixture. The prepared mixture was thermally sprayed to pass a heat source at 15000 ° C. at a speed of Mach 3 with respect to the Cu current collector to form an active material layer, thereby preparing a negative electrode for a lithium secondary battery. The thickness of the active material layer formed at this time was 20 μm.

Example 2 Preparation of Negative Electrode

A lithium secondary battery negative electrode was manufactured in the same manner as in Example 1, except that a mixture of Sn powder having an average particle diameter of 1 μm and Ti powder having an average particle diameter of 1 μm was used in a weight ratio of 50:50. It was.

Example 3: Preparation of Negative Electrode

A negative electrode for a lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of a Si powder having an average particle diameter of 200 nm and a Cu-Al alloy powder having an average particle diameter of 1 μm was used at a weight ratio of 50:50. Was prepared.

Example 4 Preparation of Negative Electrode

A negative electrode for a lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixture of SiNi alloy powder having an average particle diameter of 200 nm and Ti powder having an average particle diameter of 1 μm was used at a weight ratio of 50:50. It was.

Comparative Example 1: Preparation of Negative Electrode

Si powder having an average particle diameter of 200 nm as a negative electrode active material, polyvinylidene fluoride (PVDF) as a binder, and carbon (Super-P) as a conductive material were mixed at a weight ratio of 94/3/3, and then N-methyl-2 Dispersion in pyrrolidone produced a negative electrode slurry. The slurry was coated on a copper foil having a thickness of 10 μm, dried, and rolled to prepare a negative electrode.

Comparative Example 2: Preparation of Negative Electrode

An ingot of silicon nickel alloy was prepared by introducing a molten metal at 1400 ° C. in which 90% of silicon and 10% of nickel were completely dissolved in a copper mold. This incoat was crushed. The silicon nickel alloy particles having an average particle diameter of 0.1-10 μm and the nickel particles having an average particle diameter of 30 μm were mixed in a weight ratio of 80:20, and then mixed and pulverized using an attritor to obtain a silicon nickel alloy and The mixed particles in which nickel was uniformly mixed were obtained.

The mixed particles as an active material, acetylene black (average particle diameter 0.1 μm) as a conductive material, and polyvinylidene fluoride as a binder were mixed at a weight ratio of 80/10/10, and then added to N-methyl-2-pyrrolidone. Dispersion gave a negative electrode slurry.

The prepared slurry was applied to a copper foil having a thickness of 35 μm and dried to form an active material layer having a thickness of 60 μm. The active material layer after drying was prepressed.

The copper foil in which the active material layer was formed was immersed in a plating bath (nickel 50g / l, sulfuric acid 60g / l, temperature 40 ° C) and electrolytic plating was performed on the active material layer. The negative electrode was prepared by roll pressing the surface coating layer formed on the active material layer.

[Manufacture of test cell for charge / discharge test]

A separator consisting of a metal lithium foil counter electrode cut out into a negative electrode, the same diameter circular electrode, and a porous polypropylene film between the negative electrode and the counter electrode of Examples 1-4 and Comparative Example 1-2 was inserted, and propylene carbonate ( PC) and coin type using a solution of LiPF ₆ dissolved in a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) (PC: DEC: EC = 1: 1: 1) to a concentration of 1.3 mol / L. Half cell was prepared.

* Cathodic expansion rate

After charging the coin half battery prepared by the above method at 0.2C once, the thickness of the negative electrode was measured. The thickness of the negative electrode after charging is shown in Table 1 below as a percentage of the negative electrode thickness before charging and discharging.

* Initial charge and discharge capacity

The coin-type half-cell manufactured by the above method was charged and discharged once with 0.25C at 0.005V cut-off charge and 1.0V cut-off discharge, and the charge and discharge capacity were measured. The results are shown in Table 1 below. Indicated.

* Cycle life

The capacity after 50 cycles of charging and discharging a coin-type half-cell prepared by the above method at 0.2C is shown in Table 1 as a percentage of the initial capacity.

Cathode Expansion Rate (%) Initial charge capacity
[mAh / g] Initial discharge capacity
[mAh / g] Initial efficiency
[%] life span
[%] Example 1 30 1600 1360 85 92 Example 2 42 1200 996 83 93 Example 3 25 1800 1656 92 96 Example 4 15 1600 1296 81 89 Comparative Example 1 180 2020 1656 82 25 Comparative Example 2 156 1420 1065 75 10

As shown in Table 1, it can be seen that the cycle life characteristics show a large difference according to the porosity and the mixture density in the active material layer. That is, in the case of the battery including the electrode containing pores as in Examples 1 to 4, it can be seen that the life characteristics are significantly improved compared to Comparative Example 1 does not contain pores.

In addition, in Comparative Example 2, the peel strength was excellent, but due to the expansion of the active material due to the charge and discharge showed a lower capacity and life characteristics compared to Examples 1 to 4.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

1 is a schematic diagram schematically showing a negative electrode for a rechargeable lithium battery according to one embodiment of the present invention.

Figure 2 is a process diagram showing a simplified method of manufacturing a negative electrode according to another embodiment of the present invention.

3 is a cross-sectional view of a rechargeable lithium battery according to another embodiment of the present invention.

Claims (16)

Current collector; And An active material layer formed on the current collector; The active material layer is a solid solution of metal M (the M is Cu, Ti, Cu-X alloy, Ti-X alloy (the X is alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, and An element selected from the group consisting of a combination thereof, Cu and Ti is not selected) and a mixture thereof, and an active material capable of forming a lithium-containing compound. The method of claim 1, The active material layer is a lithium secondary battery negative electrode having a porosity of 10% by volume to 70% by volume. The method of claim 1, X is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Ru , Os, Hs, Rh, Ir, Pd, Pt, Ag, Au, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, P, As, Sb, Bi, S, Se, Te, Po And it is selected from the group consisting of a negative electrode for a lithium secondary battery. The method of claim 1, The active material may be Si, Sn, Si-Q1 alloy, Sn-Q2 alloy (Q1 and Q2 are independently of each other alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, and combinations thereof The element is selected from the group consisting of, not Si and Sn) and a mixture thereof, the negative electrode for a lithium secondary battery. The method of claim 1, Said active material is Si or Sn negative electrode for lithium secondary batteries. The method of claim 1, The active material is a negative electrode for a lithium secondary battery that is contained in more than 50% by weight based on the total weight of the active material layer. The method of claim 1, The active material is a negative electrode for a lithium secondary battery that is contained in 60 to 70% by weight based on the total weight of the active material layer. Active material powder and metal M capable of forming a lithium-containing compound (wherein M is Cu, Ti, Cu-X alloy, and Ti-X alloy (the X is alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal) , A rare earth element, and a combination thereof, and an element selected from the group consisting of Cu and Ti), and a mixture thereof) to prepare a mixture by mixing the powder; And The method of manufacturing a negative electrode for a lithium secondary battery comprising the step of thermally spraying the mixture on a current collector to form an active material layer. The method of claim 8, The active material may be Si, Sn, Si-Q1 alloy, Sn-Q2 alloy (The above Q1 and Q2 are independently of each other alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, and combinations thereof It is an element selected from the group consisting of, not Si and Sn) and a mixture thereof, the method for producing a negative electrode for a lithium secondary battery. The method of claim 8, The active material powder is a method for producing a negative electrode for a lithium secondary battery having an average particle size of 100nm to 1㎛. The method of claim 8, The metal M powder is a method for producing a negative electrode for a lithium secondary battery having an average particle size of 100nm to 1㎛. The method of claim 8, The active material powder and the metal M powder is a method for producing a negative electrode for a lithium secondary battery is mixed in a weight ratio of 30:70 to 70:30. The method of claim 8, The thermal spraying process is selected from the group consisting of plasma spraying method, arc spraying method, ultra-fast flame spraying method, gas spraying method and combinations thereof. The method of claim 8, The thermal spraying step is a method for producing a negative electrode for a lithium secondary battery that is carried out at a temperature of 10000 to 18000 ℃. The method of claim 8, The thermal spraying step is a method of manufacturing a negative electrode for a lithium secondary battery that is carried out at a spray rate of 100 to 400m / sec. The negative electrode of any one of Claims 1-7; anode; And Electrolyte Lithium secondary battery comprising a.

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